1. Field of the Invention
The present invention relates to an image transmission device for transmitting input image data to another place, an image display device for displaying image data, and an image transmission. system combining these devices.
2. Related Background Art
Some conventional systems realize electronic conferencing between remote places by transmitting images and voices to a remote place and displaying and reproducing them in the remote place. In these conventional systems, a television signal of NTSC is often used as an image signal to be transmitted.
The resolution of an image transmittable by this television signal of NTSC is not high. Therefore, even when images of slides (e.g., photographs of microscopic images) used in research meetings or meetings of academic societies in the fields of medical, chemistry, and the like are transmitted, the transmitted images do not have a satisfactory image quality legible on the receiving side. These particular applications require transmission of high-definition (or high-resolution) images. Therefore, an image transmission system by which high-definition images can be exchanged in a conference held between a plurality of remote places is necessary.
An image transmission system comprises a plurality of image transmission devices. Transmitted image data is stored in an internal frame memory of an image transmission device and displayed. The data stored in the frame memory is easily destroyed by, e.g., an erroneous operation or transmission of another image. If it is necessary to transmit the image data again, the transmission consumes time and the network is used by the retransmission. In particular, transmitting a high-definition image is a big problem because the transmission time is long.
In either case, it takes a long time to transmit high-definition images because the images have a large image data amount.
Consequently, the transmitted images cannot be displayed in real time in a remote place and this makes a conference difficult to hold.
The present invention has been made in consideration of the above situation and has as its first object to provide an image transmission system capable of immediately reviving a transmitted image even if the image is erased.
To achieve the above object, the present invention provides an image transmission system in which a plurality of image transmission devices are connected by a network, each of the image transmission devices comprising a frame memory for storing input image data from another image transmission device, and a display device for displaying an image on the basis of the data stored in the frame memory, wherein the image transmission device also stores the image data in a storage device different from the frame memory when storing the image data in the frame memory.
The present invention also provides an image transmission system in which a plurality of image transmission devices are connected by a network, each of the image transmission devices comprising a frame memory for storing input image data from another image transmission device, a display device for displaying an image on the basis of the data stored in the frame memory, and a storage device different from the frame memory, wherein the image transmission device also stores the image data in the storage device when storing the image data in the frame memory, and further comprises means for transferring the image data stored in the storage device to the frame memory if the image data stored in the frame memory is lost.
The present invention also provides an image transmission system in which a plurality of image transmission devices are connected by a network, each of the image transmission devices comprising a frame memory for storing input image data from another image transmission device, a display device for displaying an image on the basis of the data stored in the frame memory, and a storage device different from the frame memory and capable of storing a plurality of image data, wherein the image transmission device also stores the image data in the storage device with a name assigned to the image data when storing the image data in the frame memory, and further comprises means for reading out the image data stored in the storage device by designating the name and transferring the image data to the frame memory if the image data stored in the frame memory is lost.
It is the second object of the present invention to provide an image transmission system capable of preventing the transmission time from being prolonged even when transmitting a high-definition image.
To achieve the above object, in an image transmission system in which a plurality of image transmission devices capable of transmitting and receiving image data are connected by a network, the present invention provides the improvement characterized in that the system comprises an exclusive control device which, before a certain image transmission device transmits image data to another image transmission device, prohibits other image transmission device(s) from transmitting a command or image data onto the network. This system may be so constructed that when the transmission of image data from a certain image transmission device to another image transmission device is completed, the exclusive control device can release the prohibition of transmission of a command or image data from other image transmission device(s) to the network.
In an image transmission system in which a plurality of image transmission devices capable of transmitting and receiving image data are connected by a network, the present invention also-provides the improvement characterized in that each of the image transmission devices sends an exclusion command for prohibiting other image transmission device(s) from transmitting a command or image data onto the network before transmitting image data to another image transmission device.
The present invention also provides an image transmission system comprising
a plurality of image transmission devices capable of transmitting and receiving image data, and
a control unit connected to the image transmission devices to control data transmission between the image transmission devices, the control unit including exclusive control means which, while a certain image transmission device is transmitting image data to another image transmission device, ignores a command or image-data received from other image transmission device(s). The exclusive control means may be so constructed that when the transmission of image data from a certain image transmission device to another image transmission device is completed, the exclusive control means can stop ignoring a command or image data from other image transmission devices.
The present invention also provides an image transmission system comprising
a plurality of image transmission devices capable of transmitting and receiving image data, and
a control unit connected to the image transmission devices to control data transmission between the image transmission devices, the control unit including exclusive control means which, while a certain image transmission device is transmitting image data to another image transmission device, stores a command or image data received from other image transmission devices and temporarily stops execution of the command or retransmission of the image data.
The exclusive control means may be so constructed that when the transmission of image data from a certain image transmission device to another image transmission device is completed, the exclusive control means can stop storing a command or image data received from other image transmission device(s) and transmit the stored command or image data.
The exclusive control means may also be so constructed that when the transmission of image data from a certain image transmission device to another image transmission device is completed, the exclusive control means can execute the stored command or transmit the stored image data.
It is the third object of the present invention to provide an image transmission device, an image display device, and an image transmission system which can be used in a conference held between a plurality of remote places by using high-definition images.
To achieve the above object, the present invention provides an image transmission device comprising image input means for inputting image data, image transfer means for transferring a plurality of input image data from the image input means, and indicating means for transferring an indication signal for indicating at least one of the plurality of image data after the image data are transferred from the image transferring means, the indication signal comprising a signal for indicating one image data by using at least two types of names.
The present invention also provides an image transmission device comprising an input unit for inputting a plurality of externally input image data, storage means for storing the input image data from the input unit, and display means for receiving an indication signal indicating at least one of the plurality of image data, reading out the image data indicated by the indication signal, and displaying an image of the readout image data, wherein the indication signal is a signal for indicating one image data by using at least two types of names.
The present invention also provides an image transmission system comprising an image transmission device including image input means for inputting image data, image transfer means for transferring a plurality of input image data from the image input means, and indicating means for transferring an indication signal for indicating at least one of the plurality of image data after the image data are transferred from the image transferring means, and
an image display device including an input unit for inputting the plurality of image data transferred from the image transfer means, storage means for storing the input image data from the input unit, and display means for receiving the indication signal, reading out the image data indicated by the indication signal, and displaying an image of the readout image data, the indication signal comprising a signal for indicating one image data by using at least two types of names. The two types of names may be transferred at once when the indication signal is transferred. The two types of names may also be separately transferred when the indication signal is transferred.
The present invention also provides an image transmission device comprising image input means for inputting a plurality of image data having different resolutions,
image transfer means for transferring, from among the input image data, image data with a low resolution to an external device and then transferring image data with a high resolution to the external device, and
indicating means for outputting to the external device an indication signal for displaying the image data with a high resolution after the image data with a high resolution is transferred, the indication signal comprising a signal for indicating one image data by using at least two types of names.